Bitbills

According to the product's announcement Bitbills are the first physical incarnation of bitcoins.

A Bitbill is a plastic card that holds the cryptographic key that will allow the face value amount of the card to be spent. The key is on a QR code embedded within the card such that it cannot be read without the card showing evidence of tampering. Additionally, the card has a hologram affixed to ensure that the card is not a counterfeit.

The intention is that the card will be left unopened and then can be treated as money by being acceptable at face value when making a transaction in-person at a retailer, for example. At any time, the card can be opened and the funds spent through the Bitcoin payment network. Once the card has been opened it will no longer be acceptable as payment anywhere else due to the fact that the private key will have been revealed.

At the time this article was created, the ability to spend a Bitbill requires that a patch to the Bitcoin software is first in place.